Current drilling engineering applications programs generally consider only one aspect of the drilling process and therefore allow drilling optimisation in terms of only one variable. In reality, however, drilling is a highly complex and interactive process in which optimisation of one parameter in isolation can have significant and possibly detrimental effects on another. This paper describes a novel computer program, the Wellbore Fluids Model, that allows a realistic replication of the interacting processes that occur as drilling fluid flows around the wellbore; these include, for example, cuttings transport, hydraulic pressures and fluid property changes with temperature and pressure. By considering these interactions simultaneously the model can provide a more realistic foundation on which to base engineering decisions to ensure optimum rate of penetration. The paper provides a comparison of the model predictions against field measured data. A simulation which illustrates the complex interactions that occur whilst drilling is presented.

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